ROOT  AERATION  IN  RELATION  TO  PLANT  GROWTH 


BY 


MATTHEW  GEORGE  STAHL 

B.  S.  University  of  South  Africa,  1919 
M.  S.  Kansas  State  Agricultural  College,  1921 


THESIS 

SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 
FOR  THE  DEGREE  OF  MASTER  OF  ARTS  IN  BOTANY 
IN  THE  GRADUATE  SCHOOL  OF  THE 
UNIVERSITY  OF  ILLINOIS 
1922 


URBANA,  ILLINOIS 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/rootaerationinreOOstah 


/ 3 Jaz  3 * Af* 


I S2Z 

Si  l 4 

UNIVERSITY  OF  ILLINOIS 
THE  GRADUATE  SCHOOL 

July -23—  -192-2- 

I HEREBY  RECOMMEND  THAT  THE  THESIS  PREPARED  UNDER  MY 

SUPERVISION  BY Matthew  George  Stahl 

ENTITLED^  Root  Aeration  in  Relation  to  Plant  Growth. 


BE  ACCEPTED  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR 
THE  DEGREE  OF  Master  of  A rts  in  Botany 


In  Charge  of  Thesis 


dsf.14  Head  of  Department 


Recommendation  concurred  in* 


Committee 

on 

Final  Examination* 


•Required  for  doctor’s  degree  but  not  for  master’s 


TABLE  OF  CONTENTS 

I.  Introduction  - --  --  --  --  --  --  --1 

II.  Scope  of  the  Present  Work  - --  --  --  --  --  4 

III.  .Apparatus  and  Methods  - --  --  --  --  --  -4 

IV.  Experiments  on  Aeration  _--.-____-.__y 

A.  Corn  - --  --  --  - - ----7 

B.  Beans  - - - _________  iq 

C.  Barley  - --  --  --  --  --  --  13 

V.  Experiments  on  the  Effects  of  Increased  and  Decreased  Partial 

Pressure  of  Oxygen  on  the  Growth  of  Com,  Beans  and  Barley  - l4 

A.  Corn  - __________  l4 

B.  Beans  - - - _________  l£ 

C.  Barley  __  _________  17 

VI.  Experiments  on  the  Effects  of  Increased  Partial  Pressure 

of  Carbon  Dioxid  on  the  Growth  of  Beans,  Com  and  Barley  - 20 

A.  Corn  - - 20 

B.  Beans  - --  --  --  --  --  --  23 

C.  Earley  - --  --  --  --  --  -23 

VII.  Experiments  on  Sand  Cultures  - --  --  --  --  - 2^ 

VIII .  Summary  - --  --  --  --  --  --  --  --  2J 

IX.  Conclusions  - --  --  --  --  --  --  --  - 2$ 

Literature  Cited  - --  --  --  --  --  --  - 30 

Tables  -(l-13>  - --  - --  --  --  --  - 3^-42 

Figures  (1-3)  - --  --  - ---------  43-45 

Plates  (1-11)  - --  - 46-56 


ACOOWLEDGE5JIEKT 


The  apparatus  used  in  the  experiments  reported  in  this  paper  was 
devised  and  constructed  by  Dr.  C.  T-  Ilottes. 

The  writer  wishes  to  acknowledge  hi3  indebtedness  to  Dr.  Hctte3 
for  his  direction  in  outlining  and  preparing  this  report  and  also  to  thank 
him  for  his  continued  interest  and  encouragement  during  the  execution  of 
the  work. 


-1- 

ROOT  AERATION  IN  RELATION  TO  PLANT  GROWTH 
I Introduction 

Since  the  process  of  respiration  in  roots  is  identical  with  the 
respiration  found  to  occur  in  other  parts  of  the  plant,  it  is  of  fundamental 
importance  that  the  roots  be  assured  of  an  adequate  supply  of  oxygen  and  that 
undue  accumulation  of  carbon  dioxid  be  prevented. 

In  the  seventeenth  century  Malphigi  showed  that  germination  of  seeds 
could  not  take  place  in  the  absence  of  air.  An  enormous  amount  of  quantitative 
data  on  the  gaseous  exchanges  occurring  in  geminating  seeds  has  since  been 
accumulated. 

The  necessity  for  adequate  root  aeration  in  growing  crops  has  long 
been  emphasized  in  agricultural  practice  and  has  constituted  one  of  the  fund- 
amental factors  in  the  development  of  the  present  methods  of  tillage.  Pew  ex- 
periments, however,  have  been  reported  which  bear  directly  on  the  aeration  of 
the  soil  by  artificial  means  other  than  tillage.  Day  (7)  grew  barley,  oats, 
wheat  and  peas  in  stone  crocks  which  were  artificially  aerated  by  drawing  air 
through  them  from  below.  After  ten  weeks’  growth  a slight  advantage  due  to 
aeration  was  noted  in  the  case  of  barley,  wheat  and  oats.  The  peas  in  aerated 
pots  showed  considerable  increase.  Upon  repeating  the  experiments  the  follow- 
ing year,  the  results  with  barley  and  wheat  were  contradictory  and  the  effect 
of  aeration  on  peas  was  not  so  marked.  Soybeans  and  alfalfa  showed  increases 
due  to  aeration.  At  the  Hatch  Experiment  Station, Stone  (l$)  obtained  in- 
creased growth  of  lettuce  by  drawing  air  through  boxes  for  six  hours  daily. 

The  soil  atmosphere  has  been  shown  by  Russel  and  Appleyard  (17)  to 
contain  les3  oxygen  and  considerably  more  carbon  dioxid  than  the  atmosphere 
above  it.  Its  composition  is  largely  determined  by  the  biological  processes 


-2- 

cccurring  within  it.  In  addition  to  the  free  air  of  the  soil,  there  is  another 
atmosphere  dissolved  in  the  water  and  colloids  of  the  soil.  This  consists 
mainly  of  carbon  dioxid  and  nitrogen  and  has  practically  no  oxygen.  Leather  (15) 
has  shewn  that  the  soil  air  in  the  neighborhood  of  roots  may  contain  abnormally 
high  percentages  of  carton  dioxid.  Surrounding  the  roots  of  Zea  he  found  the 
air  to  contain  from  eight  to  sixteen  percent  of  carbon  dioxid  and  from  2.13  to 
thirteen  percent  of  oxygen. 

In  a series  of  researches  Livingston,  Cannon,  and  Free  (U)  have  studied 
the  direct  effects  of  growing  plants  in  soils  deficient  in  oxygen.  The  thirty 
species  studied  responded  in  different  degrees  to  diminished  partial  pressure 
of  oxygen.  In  general,  a deficiency  of  oxygen  existed  when  the  oxygen  comprised 
less  than  ten  percent  of  the  soil  air  -with  the  remainder  nitrogen.  All  species 
were  able  to  maintain  growth  when  the  oxygen  fell  as  low  as  two  percent, 
provided  that  the  amount  of  carbon  dioxid  was  not  excessive.  Growth  stopped 
and  the  roots  were  killed  if  they  were  entirely  deprived  of  oxygen. 

Since  the  extent  of  the  free  air  of  the  soil  bears  an  inverse  ratio 
to  the  amount  of  water  present,  aeration  is  being  recognized  as  a determining 
factor  in  the  ecological  distribution  of  plants. 

The  effects,  direct  and  indirect,  of  poor  aeration  have  received  con- 
siderable attention  in  studying  the  problems  of  soil  toxins  and  soil  acidity. 
Clements  (6)  claims  that  lack  of  oxygen  is  the  basic  cause  of  these  conditions. 

Sudden  and  periodic  submergence  of  roots  and  the  consequent  deleterious 
effect  on  growth,  through  interference  with  respiration  and  aeration,  have 
called  forth  considerable  research.  Bergman  (3)  in  greenhouse  experiments  has 
demonstrated  that  sudden  flooding  causes  wilting  and  death  in  Vicia  .and 
Pelargonium  but  has  no  effect  on  Ranunculus  and  Cyperus.  If  artificial  aeration 
be  resorted  to,  the  plants  recover,  form  new  roots  and  continue  growth.  He 
also  found  that  when  aeration  is  provided  the  development  of  plants  is  essen- 


-3- 


tially  as  good  with  swamp  water  as  with  nutrient  solution.  He  attributed  the 
slight  difference  observed  to  nutrition. 

Hole  and  Singh  (12)  in  experiments  with  seedlings  of  3al  (Shorea  robusta) 
found  that  poor  soil  aeration  caused  stunting  of  the  roots  and  ultimately  death 
through  the  accumulation  of  carbon  dioxid  and  lack  of  oxygen. 

Howard  and  Howard  (l4)  have  noted  a marked  aerotropisrc  of  the  roots  of 
indigo  as  the  ground  water  rises  in  the  soil.  Deficient  aeration  causes  the 
death  of  submerged  roots  and  consequent  wilting. 

lacker  (20)  found  that  the  roots  of  Lupinus  albus,  Helianthus  and  Yicia 
did  not  grow  as  vigorously  in  water  as  in  soil.  In  cultures  of  mud  the  roots 
of  Vicia  died  off  due  to  lack  of  oxygen  and  the  accumulation  of  toxic  decomposi- 
tion products.  Arker  (2)  in  following  up  these  studies  found  that  the  roots  of 
these  plants  showed  increased  growth  if  air  was  bubbled  through  the  culture 
solution.  This  he  attributed  to  the  greater  mobility  of  the  oxygen  rather  than 
an  increased  partial  pressure. 

Hall,  Brenchley  and  Underwood  (11)  have  attributed  the  superiority  of 
cultures  in  solid  media  over  water  cultures  entirely  to  the  better  aeration 
under  the  former  conditions.  By  bubbling  air  continuously  through  water 
cultures  of  barley,  he  obtained  an  increase  of  sixty  percent  in  dry  weight  over 
a period  of  eight  vveeks. 

Stiles  and  Jorgensen  (IS)  repeated  the  experiments  with  sindlar  results. 
When  Crone* s solution  was  used  with  frequent  renewal  of  cultures,  the  increase 
attributed  to  aeration  amounted  to  sixty  percent.  When  a modification  of  this 
solution  without  renewal  was  used,  fifty-three  percent  increase  was  recorded. 
With  Pfeffer’s  solution  greater  dry  weight  per  plant  was  obtained  and  the 
aerated  plants  were  heavier  by  twenty-four  percent.  Similar  results  were  ob- 
tained with  balsam.  With  buckwheat  the  difference  obtained  was  not  considered 
significant . 


-4- 

Free  ($)  grew  buckwheat  to  maturity  in  Shive’s  solution.  Sets  of 
cultures  through  which  oxygen,  nitrogen  and  air  were  continuously  bubbled  yielded 
the  same  as  untreated  cultures.  Sealing  cultures  appeared  to  exercise  no  effect. 
Cultures  treated  with  carbon  dioxid  were  killed  within  a few  days.  If  carbon 
dioxid  was  displaced  by  air  after  the  first  day,  partial  recovery  was  noted. 

Hole  (13)  has  made  the  only  attempt  to  follow  quantitatively  the  re- 
lation of  dissolved  gases  in  fluid  media.  Seedlings  of  Sal  were  set  up  in 
solutions  drawn  from  unaerated  and  aerated  pot 3.  Analysis  showed  the  former  to 
contain  more  carbon  dioxid.  After  plants  had  grown  in  the  solutions  for  three 
weeks,  the  dissolved  oxygen  and  carbon  dioxid  were  essentially  the  same  in  the 
two  series.  In  further  experiments  Sal  seedlings  were  grown  in  water  cultures 
for  eleven  weeks.  Aeration  was  accomplished  by  drawing  air  thru  the  cultures 
for  five  minutes  three  times  daily.  In  both  root  and  shoot  development  the  non- 
aerated  series  were  slightly  superior.  Analysis  showed  the  gaseous  content  of 
the  solutions  in  both  series  to  be  essentially  the  same  at  the  end  of  the  ex- 
perimental period. 

II  Scope  of  Present  Work 

The  work  reported  in  this  paper  has  been  undertaken  mainly  to  study 
the  effects  of  varying  degrees  of  aeration,to  follow  more  closely  the  gaseous 
relations  existing  under  water  culture  conditions  with  barley,  corn  and  beans 
and  to  test  the  effect  of  increased  and  diminished  partial  pressures  of  oxygen 
and  carbon  dioxid  on  these  plants. 

Ill  Apparatus  and  Methods 

( 

As  the  work  progressed,  constant  modifications  in  technique  were  found 
necessary.  In  the  experiments  on  aeration  pint  Mason  jars,  each  holding  90Qcc 
of  culture  fluid,  were  used.  These  jars  were  washed  in  cleaning  mixture,  rinsed 
in  distilled  water  and  slowly  dried  in  an  oven  before  each  experiment.  The 


-5- 

corks  usad  were  of  the  usual  type  and  were  thoroughly  coated  with  paraffin. 

The  hydrogen-ion  concentration  was  determined  by  the  colorimetric 
method  of  Clark  and  Lubs  (5)  as  modified  by  Gillespie  (10). 

Oxygen  determinations  were  made  by  the  method  of  Winkler  as  outlined  in 
"Standard  Methods  for  the  Examination  of  Water  and  Sewage"  (l). 

Samples  were  siphoned  off  into  2p0  cc.  stoppered  bottles  and  analysis 
made  immediately  after  collection.  The  dissolved  oxygen  is  reported  in  parts  per 
million.  In  the  case  of  Shive's  solution  the  dissolved  salts  materially  affected 
the  results  obtained.  In  as  much  as  the  results  from  the  five  bottles  in  each 
series  were  comparable,  it  was  not  deemed  necessary  to  attempt  correction. 

The  carbon  dioxid  is  also  reported  in  parts  per  million  and  was 
determined  in  tap  and  distilled  water  by  the  method  outlined  in  the  above  publica- 
tion (1).  Samples  of  fifty  or  one  hundred  cubic  centimetres  were  used  where  the 
carbon  dioxid  content  was  low.  In  handling  solutions  near  saturation,  only  ten 
cubic  centimetres  were  used. 

The  samples  for  gas  analysis  were  all  drawn  from  the  center  of  the 
bottle  by  means  of  the  siphon  shown  in  Plate  II  (B).  The  diameter  of  the  siphon 
and  tube  were  sufficiently  large  to  ensure  rapid  collection  of  the  sample. 

Samples  for  hydrogen-ion  determinations  were  collected  in  25cc.  stoppered  test 

tubes. 

The  standard  culture  solution  used  was  Shive's  This  was  made  up 

as  outlined  in  "A  Plan  for  Cooperative  Research  on  the  Salt  Requirements  of 
Representative  Agricultural  Plants"  (l6).  Tap  water,  distilled  water  and  a 
modification  of  Crone's  solution  were  also  used  at  various  times.  Iron  was  added 
in  the  form  of  ferric  chloride.  This  was  rendered  necessary  because  ferrous 
salts  would  interfere  with  the  oxygen  determinations.  In  long  period  cultures 
the  solution  was  periodically  tested  for  iron.  The  analysis  of  Crone's  solution 
as  used  and  of  tap  water  are  given  in  Table  I.  This  Crone's  solution  was  adopted 


-6- 

froxa  Stile3  (18)  but  only  one-fourth  the  quantity  of  iron  used  by  him  was  added. 
The  water  transpired  was  replaced  daily  after  the  loss  became  appreciable.  For 
this  purpose  distilled  water  containing  seven  to  nine  parts  per  million  of 
dissolved  oxygen  and  an  average  of  three  parts  per  million  of  carbon  dioxid  was 

used. 

The  methods  of  germination  of  seeds  and  the  technique  of  setting  up  the 
cultures  are  discussed  later  in  cases  where  departures  from  the  ordinary  procedure 

seemed  advisable. 

The  methods  of  securing  aeration  varied.  Figure  1 shows  a simple  dis- 
tribution apparatus  constructed  for  use  in  minor  experiments.  The  gas  entered 
the  cultures  through  capillary  tubing  having  an  inside  bore  of  .6  mms. 

In  the  first  experiments  with  com,  the  inlet  tubes  were  made  of  glass 
tubing  havihg  a bore  of  .6l  cm.  and  were  drawn  to  a point.  (See  Fig.  2).  For 
subsequent  experiments  the  trap  shown  in  Plate  II  (A)  was  devised.  The  capillary 
tube  (a)  conducts  the  gas  to  near  the  bottom  of  the  vessel.  The  bubbles  rise 
slowly  between  the  inner  and  outer  tube  (b)  and  are  permitted  to  escape  near  the 
surface  of  the  culture  solution  through  a small  aperture  (c).  In  this  way  slower 
and  better  aeration  was  secured  and  mechanical  disturbance  of  the  roots  was 
greatly  reduced. 

For  longer  experiments  involving  periodic  discontinuous  aeration,  the 
more  elaborate  apparatus  shown  in  Plate  I wa3  devised  and  constructed  by  Dr. 
Hottes.  Compressed  air  from  the  supply  tap  A passed  into  a reserve  tank  C 
through  a gas  washer  D into  the  four  distribution  pipes  F.  Each  distribution 
pipe  had  five  outlet  pipes  G and  an  end  cock  M.  Each  outlet  pipe  was  connected 
to  the  trap  K of  the  culture  vessel  by  glass  tubing  with  rubber  attachments 

The  gas  was  washed  and  kept  saturated  by  changing  the  distilled  water  in 
the  washer  D daily.  By  means  of  regulators  E,  which  were  connected  to  an 
electrically  controlled  contact  clock,  the  supply  of  gas  to  any  one  of  the 


-7- 


distribution  tubes  could  bs  cut  off  at  required  periods. 

The  spring  valve  B provided  for  the  regulation  of  the  pressure  which  was 
never  permitted  to  exceed  five  pounds.  Further  regulation  of  the  rate  of  bubbling 
was  attained  by  adjusting  the  release  cock  L or  the  end  taps  M.  A uniform  rate 
of  sixty  to  eighty  small  bubbles  per  minute  was  thus  ensured. 

In  the  apparatus  as  photographed,  the  connecting  pipe  has  been  removed 
between  N and  0 in  order  to  provide  for  the  increase  of  the  partial  pressvire  of 
oxygen  from  the  cylinder  P.  The  pressure  of  the  oxygen  is  regulated  in  the 
bottle  R,  and  then  passes  into  the  washer  where  it  is  mixed  with  air.  By  further 
adjustments  CO2  was  also  included  in  the  circuit. 

Since  it  was  desirable  to  check  the  bubbling  from  time  to  time,  the  usual 
technique  adopted  to  exclude  light  was  unsuitable.  The  jars  were  therefore  set 
in  galvanized  iron  cans.  (Plate  I.  T) . By  placing  a quantity  of  sand  in  the 
cans,  the  height  of  the  jar  could  be  suitably  adjusted.  A suitable  board  cover- 
ing fitting  tightly  round  the  neck  of  the  jar  served  to  exclude  the  light.  (See 
Plate  I.  V) . The  cans  were  set  cn  a table  and  were  spaced  and  arranged  so  as  to 
eliminate  the  possible  effects  of  unequal  illumination. 

IV  Experiments  in  Aeration 

A.  Com 

Experiment  I 


In  November  an  experiment  to  determine  the  effects  of  aeration 
on  com  grown  in  tap  water  was  set  up. 

Funk  Brothel's  selected  disease  free  corn  of  the  variety  Ried»s 
Yellow  Dent  was  used.  Uniform  kernels  were  chosen  and  placed  in  moist  sphagnum. 

■Hjl  % JL 

When  the  plumules  were  3 cm.  long  the  seedlings  were  transferred  from  diffuse1'' 


light  to  the  culture  vessels.  Four  series  each  containing  five  cultures  were 
used,  only  one  plant  being  used  per  jar.  Figure  2 shows  the  method  of  setting  up 


-s- 

the  cultures  in  this  experiment.  The  seedlings  were  attached  by  a rubber  band 
(A)  to  a glass  plate  (B)  with  blunted  edges.  The  corks  were  provided  with  holes 
for  the  plant,  the  inlet  tube  and  the  siphon. 

The  amount  of  dissolved  oxygen  and  carbon  dioxid  was  determined  weekly, 
a sample  for  analysis  being  collected  from  each  Jar.  The  average  result  for  each 
series  is  given  in  Table  2.  A variation  of  as  much  as  three  parts  per  million 
occurred  in  individual  cultures. 

The  plants  were  grown  for  a period  of  22  days  from  sowing.  After  two 
weeks  mold  appeared  on  kernels  of  several  cultures  and  had  an  evident  effect  on 
growth.  The  diseased  plants  were  discarded.  At  the  end  of  the  period  all  plants 
were  of  poor  color.  The  heights  and  green  weights  (Table  2)  indicate  a slight 
superiority  in  favor  of  the  ncn-aerated  cultures. 

Experiment II 

A similar  experiment  with  improved  method  of  aeration  was  set 
up  in  May  when  light  and  temperature  conditions  were  more  favorable.  Only  six 
cultures  with  surface  sterilized  seed  were  used.  Three  of  these  received  con- 
tinuous aeration.  In  the  previous  experiment,  despite  the  precaution  taken  to 
protect  the  roots  from  mechanical  disturbance  by  inserting  a glass  plate,  they 
may  have  suffered  through  agitation.  This  factor  was  entirely  absent  in  the 
second  experiment.  The  seedlings  were  set  up  before  the  first  leaf  had  emerged 
from  the  coleoptile  and  were  subjected  immediately  to  aeration. 

From  the  8th  to  the  20th  day  after  setting  up,  each  culture  was 
analysed  for  dissolved  oxygen.  By  thus  changing  2p0cc.  of  the  water  daily  and 
replacing  it  with  tap  water  containing  very  little  dissolved  oxygen,  a material 
difference  in  the  amount  of  dissolved  gas  present  was  secured.  The  daily 
analysis  for  oxygen  is  given  in  Table  5>  and-  the  results  in  Table  3* 


-9- 


Experiment  III 

In  the  next  experiment  corn  was  grown  in  Shive»s  solution  for 
40  days  from  germination.  In  all  36  cultures  were  set  up  in  series  of  six.  The 
treatments  being 

51  Control 

52  Sealed 

53  Aerated  24  hours  per  week  midway  between  culture 

renewals 

54  Aerated  15  min.  per  diem,  six  days  per  week 

£5  Aerated  9 hrs.  " n n »'  « « 

s6  Continuous  aeration. 

In  order  to  obtain  disease  free  cultures  and  prevent  excessive  diffusior 
the  usual  corks  were  not  used.  Ordinary  "ball"  Mason  jar  tops  were  provided  with 
tubulatures  as  shown  in  Plate  II  (A).  The  smaller  tubes  (m,n)  sufficed  for  the 
aeration  trap  and  to  add  or  remove  solution.  The  joints  were  made  air  tight  by 
close  fitting  rubber.  TChen  not  in  use  the  tube  (n)  was  plugged  with  a length  of 
capillary  tubing.  Before  use  the  tops  were  thoroly  waxed. 

The  seedlings  were  germinated  in  vials  made  from  test  tubes.  These 
fitted  into  the  larger  tubulatures  (o,p).  The  vials  were  cleaned  and  then  set  in 
sand  containing  60$  moisture.  Surface  sterile  seeds  were  germinated  between 
blbtting  paper  and  were  planted  in  these  vials  when  the  radicles  were  1 cm.  long. 
They  were  then  covered  with  sand  and  watered.  They  were  sealed  on  the  following 
day  by  inverting  them  in  a mixture  of  paraffin  and  vaseline,  after  which  they 
were  reset  in  moist  sand  until  shoots  had  appeared  through  the  seal.  The  vials 
were  then  carefully  removed  from  the  sand  and  only  these  having  healthy  roots 
protruding  were  3et  in  the  tubulatures  of  the  jar  tops. 

Two  plants  were  set  in  each  jar.  After  15  days,  however,  one  was 
removed  from  each  jar,  and  replaced  by  a tight-fitting  paraffined  cork. 

The  culture  solution  was  renewed  four  times  during  the  experiment,  on 
the  12th,  20th,  28th,  36th  days.  Analysis  for  dissolved  oxygen  and  hydrogen-ion 
determinations  were  made  on  these  days.  The  operations  of  setting  up  and 


-10- 

and  harvesting  were  each  spread  over  two  days,  half  of  the  cultures  im  each  series 
being  attended  to  on  each  day. 

The  relative  position  of  the  series  was  changed  from  time  to  time  dxiring 
the  experiment.  The  pertinent  data  are  given  in  Table  4. 

By  taking  measurements  of  the  longest  leaf  and  of  the  total  leaf  length, 
obtained  by  adding  the  measurements  of  each  leaf  from  base  to  tip,  the  growth  of 
each  plant  was  followed.  Using  the  longest  leaf  or  the  total  leaf  length  as 
criteria  of  growth^the  range  of  individuals  from  the  various  series  overlap  con- 
siderably. Their  averages  show  little  difference  when  plotted  on  paper.  In  dry 
weight  there  is  no  significant  difference  between  the  series. 

B . Experiments  with  Beans 

In  these  experiments  the  variety  Extra  Early  Refugee , supplied  by 
the  Vaughan  Seed  Company,  Chicago,  was  used. 

Experiment  I 

In  the  first  experiment  seeds  weighing  35^  to  3&0  mgs.  v/ere 
selected.  The  seeds  were  set  to  germinate  in  moist  clean  sand  in  diffuse  daylight. 
When  the  hypocotyls  were  4 to  5 cms.  long,  ten  seedlings  were  selected  and  set  up 
in  the  usual  manner.  The  cultures  were  left  in  diffuse  daylight  and  the  shoots 
kept  moist  by  inverted  jars  until  the  first  leaves  were  open  and  the  epicotyls 
began  to  elongate.  They  were  then  attached  to  the  apparatus  and  five  were  con- 
tinuously aerated.  The  plants  were  grown  to  maturity  in  Shive*s  solution. 

All  the  plants  made  healthy  growth  and  no  difference  between  the 
series  was  noticeable  up  to  the  time  of  flowering.  Flowers  appeared  in  both 
series  at  approximately  the  same  time.  Each  plant  bore  from  seven  to  nine  flowers. 
The  number  of  pods  set  per  plant  varied  from  one  to  four  in  the  aerated  seried. 

In  the  non-aerated  series  all  the  plants  had  two  or  three  pods.  The  leaves  which 
fell,  as  the  plants  reached  maturity,  were  collected  and  preserved.  The  culture 
solution  was  renewed  on  the  loth,  2l<i'h,  25th,  3^th  days  after  germination.  In 


renewing  the  cult-ore  solution  the  cork  and  plant  were  lifted  from  the  jar  and 
quickly  placed  in  the  new  jar,  which  had  previously  been  filled  with  fresh 

solution. 

Determinations  of  the  hydrogen-ion  concentration  and  of  the  dissolved 
oxygen  were  made  from  the  solution  removed  on  each  of  these  days.  The  hydrogen- 
ion  concentration  had  been  changed  an  equal  amount  in  both  series  and  no 
differences  could  be  attributed  to  the  effects  of  aeration.  The  dissolved 
oxygen  in  the  aerated  series  was  generally  higher  by  one  to  two  p>arts  per 
million. 

The  cultures  were  taken  down  when  the  x-*ods  began  to  dry  and  the 
leaves  turned  yellow.  From  the  data  on  the  green  weight  presented  in  Table  6 
and  the  photographs  on  Plate  3>  it  can  be  seen  that  the  plants  in  the  aerated 
series  matured  slightly  earlier  than  in  the  non-aerated  series.  The  dry  weight 
determinations  show  that  both  in  the  tops  and  roots  the  aerated  plants  were 
superior.  There  was  little  noticeable  difference  between  the  length  of  roots  in 
the  two  series.  This  is  in  contrast  with  the  results  of  the  next  experiment,  in 
which  the  roots  were  not  disturbed  by  renewal  of  the  solution. 

Experiment  II 

In  this  experiment  twenty  cultures  were  divided  into  two 
series  of  ten  each.  The  first  series  received  continuous  aeration.  The  plants 
were  grown  up  to  the  time  of  flowering.  Half  of  the  number  in  each  series  were 
harvested  on  May  1st,  and  the  remainder  on  May  7th.  The  results  appear  in 

Table  7. 

In  this  experiment  the  culture  solution  (Shive’s  R jCo)  was  not  re- 
newed. There  appeared  a distinct  difference  in  the  extent  of  the  root  develop- 
ment. This  is  clearly  shown  in  Plates  4 and  5*  In  the  dry  weights  the  aerated 
series  were  superior.  The  dry  weight  of  the  root3  particularly  shows  a re- 
markable increase  which  can  be  attributed  to  aeration. 


-12 


Experiment  III 

In  order  to  compare  the  growth  of  beans  in  Shive's  solution 
and  Crone's  solution  twenty-three  cultures  were  used. 

For  this  experiment  the  seeds  were  germinated  in  sphagnum  until  three 
days  old.  They  were  then  transferred  to  paraffined  cheesecloth  stretched  tightly 
over  flowing  tap  water.  After  two  days  the  water  was  replaced  by  Crone's 
solution  diluted  to  one-fifth  of  its  normal  strength.  On  the  seventh  day  the 
solution  was  replaced  by  full  strength  solution.  .After  a further  period  of 
twenty-four  hours  the  young  plants  were  transferred  to  Mason  jars  and  were  set  up 
in  the  usual  manner.  Twenty  jars  contained  Crone’s  solution  and  the  remaining 
three  had  Shive's  solution.  Iron  was  added  to  all  the  cultures  on  the  tenth  day 
and  continuous  aeration  was  started  in  ten  of  the  jars  containing  Crone's 
solution. 

The  earlier  growth  of  the  tops  was  good  in  all  the  cultures.  After  the 
twenty-fifth  day,  however,  the  tender  parts  of  the  plants  began  to  shrivel  and 
die.  The  plants  were  therefore  harvested  on  the  27th  day,  Only  seven  cultures 
in  each  series  of  Crone’s  solution  were  harvested. 

From  the  beginning  the  roots  in  Crone’s  solution  made  very  poor  growth. 
They  were  stubby,  profusely  branched  and  of  a slightly  brownish  color.  There 
was  little  noticeable  difference  between  the  aerated  and  the  control  series  in 
Crone '3  solution.  In  Shive's  solution  the  root  growth  was  similar  to  that 
observed  in  previous  experiments.  After  the  25th  day  the  plants  in  Crone's 
solution  began  to  produce  new  roots. 

Plate  6 shows  the  comparative  root  systems  in  the  two  solutions.  The 
photograph  was  taken  several  days  after  the  remaining  plants  were  harvested.  The 
jar  in  the  center  shows  the  extent  of  the  secondary  root  development  at  that 
time,  while  the  jar  on  the  right  shows  the  appearance  of  the  roots  in  the  average 
culture  at  the  time  of  harvest. 


-13- 


The  results  of  the  experiment  presented  in  Table  S show  distinctly  the 
difference  in  the  root  development  in  Shive’s  and  Crone’s  solutions.  In  dry 
weight  the  tops  in  Crone's  solution  were  slightly  better  in  the  aerated  series. 

C.  Experiments  with  Barley 

Experiment  I 

For  this  experiment  a selected  strain  of  barley  was  obtained 
from  the  Plant  Breeding  Department  of  the  University  of  Illinois.  The  seeds  were 
germinated  by  the  method  described  in  ”A  Plan  for  Cooperative  Research  on  the 
Salt  Requirements  of  Representative  Agricultural  Plants”  (l6).  The  method  of 
setting  up  the  cultures  is  shown  in  Plate  2.  Shive's  E^Cg  solution  was  used  and 
was  renewed  once  only. 

Uniform  seedlings  from  the  germinator  were  washed  in  a shallow  pan  con- 
taining one -fifth  normal  nutrient  solution.  They  were  then  lowered  into  the 
vials  (Plate  2 C)  until  the  kernels  rested  on  the  bottom  of  the  vials,  and  the 
roots  were  freely  suspended  in  the  culture  solution.  They  were  then  adjusted  so 
that  the  kernels  were  just  above  the  solution.  The  plants  were  held  in  place  by 
cotton  plugs.  After  the  third  leaf  appeared  the  plugs  were  adjusted  to  permit 
titlers  to  develop  freely.  Two  plants  were  grown  in  each  pint  jar.  The  plants 
made  good  growth  in  all  the  cultures.  After  the  fourth  week  a few  leaves  became 
rusted  and  one  plant  in  each  series  became  infected  with  mold.  The  cultures 
containing  them  were  therefore  discarded. 

The  plants  were  measured  and  harvested  on  the  57th  day  after  they  were 
set  out  to  germinate.  At  thi3  time  the  amount  of  root  growth  appeared  about  the 
same  in  both  series.  The  tops  in  the  aerated  series  appeared  more  vigorous.  In 
harvesting  the  plants  the  tops  in  each  culture  were  taken  separately.  Since  the 
roots  of  the  two  plants  in  each  jar  had  intertwined,  no  attempt  was  made  to 
separate  them.  The  results  appear  in  Table  S and  show  that  the  aerated  cultures 
had  produced  more  leaves  and  a greater  dry  weight. 


-14 


V.  Effects  of  Increased  and  Decreased  Partial  Pressure  of  Oxygen  on 

the  Growth  of  Corn,  Beans  and  Barley 

The  experiments  reported  in  this  section  were  -undertaken  in  an  attempt 
to  follow  more  closely  the  relation  existing  "between  the  concentration  of  dissolved 
oxygen  and  the  rate  of  growth. 

A.  Com 

In  these  experiments  seedlings  with  erect  stems  and  straight  roots  were 
deemed  necessary.  To  this  end  the  use  of  the  ragdoll  wa3  resorted  to.  Surface 
sterilized  seedlings  were  placed  in  sterile  ragdolls  for  three  to  five  days. 

They  were  removed  "before  sufficiently  large  to  suffer  root  or  shoot  injury  and 
were  placed  in  diffuse  light  until  chlorophyll  had  developed. 

Experiment  I 

Uniform  seedlings  were  selected  when  the  coleoptyje  was  2.5 
cms.  long  and  the  roots  from  7.5  to  8 cms.  long.  Two  were  then  set  up  in  each  of 
a series  of  calcium  chloride  cylinders  and  were  held  in  position. by  means  of  a 
cotton  plug.  A strip  of  filter  paper,  about  two  centimeters  in  breadth,  was 
placed  inside  the  vessel  and  served  to  draw  up  sufficient  moisture  for  the  de- 
veloping seedlings.  The  portion  of  the  cylinder  below  the  construction  was 
filled  with  water.  The  gas,  which  wa 3 supplied  through  the  aperture  near  the 
base  of  the  cylinder,  was  thus  bubbled  through  water  before  coming  in  contact  with 
the  roots. 

Of  the  five  cylinders  used,  two  were  supplied  with  a slow  current  of 
oxygen  from  the  small  distribution  apparatus,  two  were  attached  to  the  air  supply 
and  the  remaining  one  served  as  a control. 

In  the  first  fifteen  hours  the  roots  in  all  vessels  had  increased  from 
2 to  2.5  cms.  as  measured  on  the  outside  of  the  vessel.  After  forty  hours  an  in- 
crease of  8.2  cm.  was  noted  in  those  attached  to  the  oxygen  apparatus.  The  roots 
had  grown  down  through  the  constriction  of  the  cylinder  and  had  entered  the  water 


-15- 


where  a slight  curvature  had  taken  place.  In  the  first  3 cms.  below  the  kernel 
small  branch  roots  varying  in  length  from  .2  to  .S  cm.  had  been  produced.  Below 
this  was  a region  of  5 cm.  bearing  abundant  root  hairs.  The  end  region  of  3*2 
cms.  (2.S  of  which  wa3  under  water)  was  entirely  free.  In  the  cylinders  attached 
to  the  air  supply  essentially  the  same  behavior  was  noted  and  the  roots  had  in- 
creased an  average  of  7»S  cms.  After  making  an  initial  growth  of  2.6  cms.  the 
roots  in  the  control  vessel  became  injured  through  lack  of  moisture. 

Experiments  in  which  the  portion  of  the  cylinders  above  the  constriction 
were  filled  with  moist  sphagnum  gave  the  same  results. 

From  these  experiments  it  may  be  concluded  that  the  roots  of  corn, 
when  grown  in  an  atmosphere  which  is  moving  continuously,  do  not  show  any  increase 
in  the  amount  of  growth  if  the  air  is  enriched  with  oxygen. 

Experiment  II 

In  the  next  experiment  selected  corn  seedlings  of  the  same  size 
were  set  up  in  tall  glass  cylinders  26  cms.  in  height  and  having  an  internal 
diameter  of  2.6  to  3 cms.  Each  vessel  contained  about  120  ccs.  of  distilled 
water.  The  seedlings  were  secured  in  the  vessel  by  means  of  cotton  plugs  loosely 
wrapped  around  the  coleoptyle  and  were  adjusted  so  that  the  kernels  were  .5  cm. 
above  the  level  of  the  water. 

Ten  cultures  were  set  up.  In  five  cultures  the  dissolved  oxygen  con- 
tent was  6.2  to  g.4  parts  per  million,  while  in  the  remainder  this  had  been  in- 
creased to  34.2  p.p.M.  by  passing  oxygen  into  a ten  litre  bottle  containing  four 
litres  of  water  and  shaking  thoroughly.  In  order  to  maintain  this  difference  in 
dissolved  oxygen  the  plugs  were  sealed  with  vaseline  and  the  water  in  all  cultures 
wras  renewed  at  intervals  of  20  to  24  hours.  For  analysis  the  contents  of  each 
series  of  cylinders  was  poured  into  a litre  flask  and  2^0  ccs.  siphoned  off  and 
analyzed. 

The  results  are  summarized  below  and  indicate  no  difference  due  to  the 


-16- 


higher  percentage  of  dissolved  oxygen. 

Length  in  erne. 


June  12th 

6 p.m. 

June  17th  6 p.m. 

Increase 

Root 

Shoot 

Root 

Shoot 

Root 

Shoot  OS 

Series  1 

14.1 

4,60 

2S.75 

20.6 

14.65 

16.0  8.4 

Series  2 

13. s 

4.54 

28.52 

20.25 

14.72 

15.72  2L6 

At 

the  time  of 

taking  the 

cultures  down, 

the  main  roots 

had  made 

con- 

siderable  growth  and  had  produced  branch  roots  from  2 to  5 cms.  in  length.  Fo 
class  difference  in  the  length  of  these  branches  was  evident.  The  secondary  roots 
had  elongated  from  15  to  20  cm3.  Throughout  the  period  of  growth  the  increments 
were  noted  from  time  to  time  by  marks  on  the  exterior  of  the  cylinders.  These 
shewed  that  the  amount  of  growth  in  periods  ranging  from  5 to  20  hours  was 
uniform  in  both  series.  Measurements  of  the  tops  from  the  tip  of  the  coleoptyle 
to  the  end  of  the  longest  leaf  were  made  at  intervals.  The  amount  of  increase 
was  approximately  the  same  in  both  series. 

E.  Experiments  with  Eeans 

Selected  seeds  were  germinated  in  sphagnum  until  the  radicle  was  2. 5 
cms.  long.  They  were  then  transferred  to  25 0 cc.  bottles  with  narrow  necks  and 
were  secured  in  position  by  means  of  cotton  plugs.  After  three  days  in  a moist 
chamber  in  diffuse  light,  five  bottles  were  attached  tc  the  small  distribution 
apparatus  as  shown  in  Figure  1 (A).  By  bubbling  oxygen  through  them  the  amount 
of  this  gas  in  solution  was  maintained  between  l4  and  33  p.p.M.  After  three 
weeks  growth  in  Crone's  solution  there  was  no  apparent  difference  due  to  treat- 
ment with  oxygen.  Dry  weight  determinations  showed  more  individual  variability 
within  the  series  than  class  variation  between  the  series. 

Four  seedlings  which  were  injured  by  the  removal  of  all  secondary  roots, 
when  these  had  attained  a length  of  3 centimeters,  showed  more  rapid  root 
production  when  grown  in  water  rich  in  oxygen. 


C . Experiments  with  Barley 

For  these  experiments  grains  of  Hull  ess  barley  obtained  from  the 
Vaughan  Seed  Company,  Chicago,  were  used.  The  seeds  were  carefully  selected  and 
sterilized  by  immersion  for  twenty  minutes  in  chloramene  T.  They  were  then 
washed  twice  in  distilled  water  and  placed  in  a sterilized  ragdoll.  The  ragdolls 
were  set  in  a I50C  constant  temperature  case  for  four  days  until  roots  up  to  2.5 
cm.  were  developed.  They  were  then  transferred  to  cheesecloth  over  a pan  of 
freshly  boiled  distilled  water,  at  room  temperature, and  germination  was  permitted 
to  continue  until  the  roots  were  6 cms.  long  and  the  coleoptyle  3*5  cms.  long. 
Seedlings  were  then  selected  for  uniformity  and  were  set  in  a pan  of  distilled 
water  from  which  they  were  transferred  to  the  various  culture  vessels.  Where 
nutrient  solution  was  used  the  seedlings  were  placed  in  1/10  normal  solutions  for 
a few  hours  prior  to  setting  up.  All  cultures  were  placed  in  diffuse  daylight 
for  twenty-four  hours  at  a temperature  of  22  to  25°C.  After  which  they  were  sub- 
mitted to  treatment. 

Experiment  I 

Four  seedlings  we~e  each  measured  and  set  in  a 250  cc. 
Erlenmeyer  flask  containing  tap  water.  In  a series  of  five  flasks  the  dissolved 
oxygen  was  maintained  between  16  and  p.p.M.  by  renewing  the  solution  every 
twenty-four  hours.  In  the  second  series  of  five  cultures  the  oxygen  was  kept 
below  2 p.p.M.  by  daily  renewal  with  tap  water  containing  .1  to  .4  p,p%M.  The 
seedlings  were  secured  in  position  by  means  of  cotton  plugs  wrapped  around  the 
coleoptyles  and  were  placed  so  that  the  kernels  were  about  half  a centimeter 
above  the  level  of  the  water.  Renewal  of  the  water  was  affected  by  lifting  the 
plugs  from  the  old  flasks  to  new  ones  containing  fresh  water.  Analysis  for 
dissolved  gases  were  made  by  compounding  duplicate  samples  from  each  series  of 
discarded  flasks. 

After  six  days  each  seedling  was  again  measured.  At  the  end  of  this 


-18- 


period  a marked  difference  in  the  amount  of  growth  in  the  tops  was  noticeable. 
From  the  table  below  it  can  readily  be  seen  that,  in  the  length  of  both  the  first 
and  the  second  leaves,  the  cultures  containing  the  higher  amount  of  dissolved 
oxygen  were  superior. 

It  would  thus  appear  that  the  seedlings  in  the  lower  series  had  an  in- 
sufficient supply  of  oxygen  even  though  this  supply  had  been  constantly  renewed. 


June 

June  13th 

Dissolved  Op 

Culture 

Root 

Shoot 

Root 

Shoot 

average 

cms. 

cms. 

cms. 

1 

2 

ppm. 

1 

9.3 

6.0 

11.1 

15.4 

10.3 

1.2 

2 

9-33 

5.56 

11.2 

14.62 

12.0 

1.2 

3 

10.4 

53 

11.8 

15.1 

11.7 

•3 

4 

10.4 

5.4 

12.5 

13.3 

15.1 

.9 

5 

9.  8 

5.7 

12.4 

14.6 

10.7 

6 

10.3 

5-2 

11.45 

16.  s 

13.2 

21. 0 

7 

10.2 

6.1 

12.2 

17.85 

15.2 

21.0 

8 

9.7 

5-1+ 

11.6 

16.2 

15.3 

13.7 

3 

10.1 

5.8 

12.2 

17.2 

15.4 

IS. 7 

10 

9-3 

5.2 

13.6 

15.1 

14.2 

Experiment  II 

In  order  to  test  this  further,  ten  cultures  were  set  up  in 
Crone’s  solution.  Five  seedlings  were  set  in  corks  in  the  usual  manner  in  pint 
Mason  jars.  The  oxygen  content  in  a series  of  five  was  kept  high  by  renewal  of 
the  solution  every  forty-eight  hours.  The  solution  removed  was  shaken  up  with 
oxygen  and  replaced  two  days  afterwards.  The  experiment  was  carried  on  over  a 
period  of  three  weeks.  The  cultures  were  kept  at  15°C. 

At  the  end  of  the  period  no  difference  was  noticeable.  Growth,  how- 
ever, had  been  very  slow,  owing  to  the  comparatively  lo w temperature. 

Experiment  III 


In  this  experiment  the  effect  of  an  increased  partial 
pressure  of  oxygen  was  again  studied.  Eight  cultures  were  set  up  in  distilled 
water,  eight  in  tap  water,  six  in  Shive’s  solution  and  six  in  Crone’s  solution. 


t 


-IS- 
AS soon  as  the  shoots  were  6 cms.  long,  half  the  number  of  cultures  in  each  series 
was  attached,  to  the  distribution  apparatus  and  were  subjected  to  continuous  aera- 
tion with  air  enriched  with  oxygen.  Analyses  for  dissolved  oxygen  were  made  daily. 
Two  control  cultures  in  tap  water  were  used  for  this  purpose  and  a sample  was 
collected  from  each  on  alternate  days.  In  this  way  the  oxygen  content  was  kept 
at  16  to  20  p.p.M.  in  half  of  the  cultures  while  the  remainder  had  from  6 to  2.5 
parts  per  million. 

The  plants  made  good  growth  in  all  solutions.  After  one  week  very 
distinct  differences  in  the  nature  of  the  roots  became  apparent.  The  pictures 
(shown  in  Plates  7 - 10)  were  taken  shortly  after  the  root  development  became 
distinctive.  These  differences  were  much  more  marked  when  the  cuj tures  were 
taken  down  after  thirteen  days  treatment.  At  that  time  the  following  notes  were 
made : 

"In  distilled  water  (AP).  Root  development  quite  extensive,  but  not  a3 
much  as  in  any  other  series.  Root  hair  development  pronounced  at  points  of 
curvature.  Laterals  developed  chiefly  in  lower  half  of  roots  and  appear  better 
in  the  aerated  series  (APA). 

Tap  water  (T).  Root  growth  characteristic.  Main  roots  yellowish  in 
color  with  well  marked  root  hairs.  Branches  long  and  white  in  color.  Branches 
slightly  shorter  in  non-aerated  series. 

In  Stave's  solution  (SH).  Roots  long,  white  with  abundant  characteristic 
long  branches.  Featherlike.  Root  hairs  developed  chiefly  at  points  of  curvature. 
No  marked  differences- between  aerated  and  non-aerated. 

Crone's  solution  (Cr).  On  the  whole  the  roots  in  this  series  are  very 
much  shorter  than  in  others.  Branching  occurs  chiefly  along  lower-most  third  of 
the  roots  in  a comb  like  manner.  Branches  stubby  and  thicker  than  in  all  other 
series.  Root  hairs  well  developed". 


It  can  thus  be  seen  that  in  the  four  treatments  the  external 


-20- 

morphology  of  the  root  was  distinctive  and  was  determined  ty  the  respective 
nutrient  medium.  No  difference  could  be  attributed  to  the  increased  partial 
pressure  of  oxygen.  The  roots  in  Crone’s  solution  developed  characteristics 
analagous  to  those  shown  by  beans  in  the  same  solution.  In  the  tops  there  was 
little  to  choose  between  Crone's  and  Shive's  solution.  Tap  water  gave  good 
growth,  the  leaves  being  slightly  narrower  and  more  harsh  to  the  touch. 

The  plants  were  harvested  after  thirteen  days  treatment,  or  twenty  days 
after  placing  in  the  ragdoll.  The  average  height  for  each  culture  was  determined 
by  an  exact  measurement  of  each  seedling.  The  weights  were  determined  on  an 
analytical  scale  and  bear  out  the  observation  that  the  increased  amount  of 
dissolved  oxygen  had  not  stimulated  the  plants  in  any  way.  The  results  appear  in 
Table  10. 

VI . The  Effects  of  Increased  Partial  pressure  of  Carbon  Dioxid  on 

The  Growth  of  Corn,  Beans  and  Barley 

A.  Corn 

In  order  to  test  the  effect  of  high  concentrations  of  carbon  dioxid  over 
short  periods  of  time  on  the  growth  of  com,  the  following  experiment  was  under- 
taken. 

Experiment  I 

Five  seedlings  were  set  up  in  each  of  four  pint  Mason  jars.  The 
height  of  each  seedling  was  measured  shortly  after  the  first  leaf  had  emerged. 

The  treatment  accorded  the  various  jars  was  as  follows: 

Numbers  1 and  2 were  attached  to  the  distribution  apparatus.  The  tap 
water,  in  which  they  were  grown,  was  rapidly  brought  up  to  saturation  by  bubbling 

Jt 

carbon  dioxid  through  them.  After  fifteen  hours  these  cultures  were  disconnected 
and  the  water  in  Number  2,.  was  changed. 

On  the  second  day  Number  3 was  saturated  with  carbon  dioxid  for  three 


-21- 

hours.  The  carbon  dioxid  was  then  expelled.  On  the  fifth  day  it  was  again 
treated  with  carbon  dioxid  for  twenty-two  hours  and  on  the  sixth  day  air  was 
bubbled  through  it  for  two  hours.  The  fourth  bottle  was  used  as  a control  and 
received  no  treatment.  The  heights  of  the  plants  in  each  bottle  were  measured 
after  1J , 29 , 43,  96  hours  and  then  at  every  twenty-four  hour  period  for  a week. 

The  average  height  per  culture  at  each  period  of  measurement  is 
presented  in  Table  11,  together  with  the  average  increment  in  growth  per  culture. 

In  figure  3 the  results  are  plotted  together  with  the  treatment.  When  the 
cultures  ware  set  up  the  first  leaf  had  just  emerged  from  the  coleoptyle.  After 
twenty-three  hours  of  treatment  it  was  observed  that  the  first  leaf  had  unfolded 
and  the  second  was  appearing  in  all  plants  of  cultures  4 and  2,  while  in  culture 
3 the  development  was  not  as  far  advanced.  The  roots  of  1 and  3 had  only  increased 
half  the  amount  noted  in  the  control.  The  root 3 of  culture  4 had  produced 
branches  while  none  had  developed  in  Number  1.  Numbers  2 and  3 were  intermediate. 
Thirty-six  hours  later  the  roots  in  all  the  cultures  had  branches. 

After  an  additional  forty-eight  hours  there  was  little  apparent 
difference  between  cultures  2,  3 and-  4.  The  roots  had  lengthened  considerably. 

In  Number  1,  the  elongation  of  the  main  roots  had  apparently  ceased,  though 
branches  continued  to  grow.  The  seminal  roots  had  elongated  considerably. 

After  one  week  all  the  plants,  with  the  exception  of  one  in  culture  1, 
had  produced  three  leaves. 

An  analysis  of  the  data  seems  to  indicate  that  the  initial  treatment 
for  seventeen  hours  had  a slight  depressing  effect  in  culture  2,  but  that  this 
was  overcome  after  four  days.  The  initial  treatment  for  twenty-nine  hours  in 
culture  1 had  a slight  depressing  effect  - almost  identical  with  that  observed  in 
the  second  culture.  Since,  however,  it  was  subject  to  carbon  dioxid  (-with  falling 
concentration)  for  an  additional  period  of  hours,  the  effect  was  more  permanent 
and  could  be  plainly  read  in  the  developing  plants. 


-22- 

In  number  3 the  initial  rate  of  growth  was  almost  identical  with  that  in 
the  control.  Treatment  for  four  hours  caused  a slight  retardation.  A second 
treatment  for  thirty-six  hours  caused  a sudden  drop  in  the  growth  rate. 

In  the  case  of  the  roots,  the  effect  of  the  carbon  dioxid  can  be  seen  in 
an  initial  suppression  of  branch  roots  and  a retardation  of  the  rate  of  elongation 
The  injured  roots  function  and  produce  branches  after  a short  time.  The  main 
burden  of  absorption,  however,  appears  to  be  thrown  on  to  the  seminal  roots  which 
develop  rapidly. 

Experiment  II 

The  effect's  of  lower  concentrations  of  carbon  dioxid  on  corn 
were  studied  in  the  following  manner. 

Eleven  com  seedlings  were  set  up  in  tap  water  as  described  in  Experiment 
II  of  the  previous  section.  The  vessels  were  divided  into  three  series  when  the 
first  leaf  had  emerged  from  the  ccleoptyle  and  was  about  1 cm.  long.  The  first 
two  series  of  four  seedlings  each  were  attached  to  the  distribution  apparatus.  A 
mixture  of  gases  was  then  3lowly  bubbled  through  the  vessels  so  that  the  amount 
of  dissolved  carbon  dioxid  was  maintained  in  the  neighborhood  of  150  p.p.M.  in 
the  first  series  and  75  to  100  p.p.M.  in  the  second  series.  The  third  series 
was  used  a3  a control  and  received  no  treatment. 

The  height  of  the  seedling  from  the  top  of  the  coleoptyle  to  the  tip  of 
the  leaf  was  measured  daily  over  a period  of  one  week.  The  average  height  of 
each  series  together  with  the  daily  increments  in  growth  and  the  carbon  dioxid 
treatment  are  given  in  Table  12.  Some  days  after  treatment  was  suspended  some 
of  the  kernels  showed  signs  of  disease  and  it  is  not  known  what  effect  this  has 
had  on  growth.  In  the  amount  of  root  development  there  was  little  difference 
noticeable  in  the  cultures. 

It  may  be  concluded  that  corn  grown  in  tap  ’water  containing  carbon 
dioxid  in  amounts  up  to  15$  saturation  dees  not  exhibits afty  immediate  signs  of 


-23- 


toxicity.  The  conclusion  is  further  substantiated  by  the  measurements  made 
thirteen  days  (31  6 hours)  after  the  cultures  were  set  up.  The  length  of  the 
tallest  leaf,  the  length  of  the  main  root  and  the  average  length  of  the  seminal 
root 8 are  given  in  the  table.  The  variations  found  are  probably  individual  end 
hence  cannot  be  correlated  with  the  increased  partial  pressure  of  carbon  dioxid. 

B.  Experiments  with  Beans 

Eight  bean  plants  which  had  grown  in  Crone 1 3 solution  up  to  the  time  of 
flowering  were  used  to  test  the  effect  of  carbon  dixid  on  this  plant.  Six  of 
these  were  divided  into  two  series  of  three  each.  Prior  to  treatment  these  series 
had  an  average  transpiration  rate  of  ccs.  and  23  ccs.  per  plant  per  day.  One 
series  was  saturated  with  carbon  dioxid  for  a period  of  three  hours.  At  the  end 
of  this  period  the  plants  showed  signs  of  wilting  and  they  were  therefore  dis- 
connected. By  the  following  morning  they  had  recovered  and  could  not  be  dis- 
tinguished from  the  control  series.  After  a period  of  twenty-four  hours  they  were 
again  treated  with  carbon  dioxid  for  twenty-four  hours.  On  the  following  day  all 
the  carbon  dioxid  was  expelled  by  aeration. 

In  the  treated  series  the  transpiration  rate  had  dropped  nearly  fifty 
percent  after  the  third  day  of  treatment.  The  individual  plants  did  not  respond 
to  the  3ame  degree.  After  four  days  the  leaves  began  to  yellow  and  after  one  week 
two  of  the  plants  had  been  killed,  the  remaining  one  lost  most  of  the  leaves  but 
produced  new  roots  and  continued  to  live.  Another  plant  which  had  been  treated 
for  four  hours  only  had  lost  all  its  older  leaves  but  recovered  sufficiently  to 
start  new  roots  and  produce  new  leaves. 

The  toxic  effect  of  carbon  dioxid  on  fully  developed  bean  plants  is 
very  marked. 

C.  Experiments  with  Barley 

In  order  to  test  the  effect  of  carbon  dioxid  on  the  growth  of  barley, 
duplicate  cultures  were  set  up  in  distilled  water,  tap  water,  Shive’s  solution, 


-24- 


Crone’s  solution  and  Crone’s  solution  without  iron.  The  cultures  were  set  up  when 
the  coieoptyles  were  4 to  4.5  cm.  long  and  the  roots  6.5  cm.  long.  After  a day  in 
diffuse  light  the  heights  from  the  corks  were  measured.  One  culture  in  each  of 
the  solutions  was  then  attached  to  the  distribution  apparatus  and  a mixture  of  air 
containing  150  p.p.M.  of  carbon  dioxid  ms  passed  through  them  for  a period  of 
twenty-four  hours,  after  which  they  were  treated  with  carbon  dioxid  alone  for  a 
period  of  eighteen  hciirs.  Some  of  the  carbon  dioxid  was  then  lost  by  diffusion 
during  a further  period  of  twenty-four  hours,  after  which  it  was  rapidly  expelled 
by  passing  air  through  the  cultures.  After  twenty-four  hours  aeration,  the 
cultures  were  left  to  stand.  Measurements  of  the  seedlings  were  made  at  periods 
of  13,  36,  54,  74  hours  after  treatment  was  started  and  at  intervals  of  twenty-four 
hours  thereafter  until  the  seventh  day.  The  height  of  each  seedling  and  leaf  was 
measured  to  the  nearest  millimeter;  six  measurements  were  made  on  each  jar.  Sy 
measuring  a known  seedling  twice,  a check  on  the  accuracy  of  the  measurements  was 
maintained.  These  show  that  the  effect  of  the  carbon  dioxid  is  noticeable  within 
twenty-four  hours,  though  growth  continued  in  all  cultures.  The  extent  of  the 
injury,  however,  was  not  sufficient  to  outweigh  the  differences  due  to  nutrition 
in  the  various  solutions. 

The  second  leaves  in  all  the  treated  cultures  appeared  later  than  in 
the  corresponding  control  cultures.  One  week  after  treatment  commenced,  little 
difference  was  noticeable  in  the  tops  of  the  cultures  in  the  nutrient  solutions, 
though  the  treated  cultures  were  in  every  case  slightly  shorter. 

In  the  control  cultures  the  various  solutions  again  called  forth  the 
characteristic  growth  habits  of  the  roots  which  had  been  noted  in  a previous  ex- 
periment . 

In  the  treated  cultures  branches  were  observed  in  Shivs ’s  solution  and 
tap  water.  These,  however,  were  shorter  than  in  the  corresponding  control  culture. 
In  the  Crone’s  solution  no  branches  were  observed  at  this  time.  The  development  of 


-25- 

root  hairs  however  was  extensive.  In  distilled  water  the  roots  were  longer  in  the 
control  cultures.  On  the  fourteenth  day  after  setting  up  the  root  characteristics 
were  more  pronounced.  Branches  had  grown  rapidly  in  the  treated  cultures  of 
Shiva's  solution  and  tap  water.  The  roots  in  treated  cultures  of  Crone's  solution 
had  produced  numerous  branches  above  the  level  of  the  water. 

After  twenty  days  the  tops  in  distilled  ivater  were  dying  and  showed  little 
solution 

difference.  In  Shive' sAand  tap  water  the  root  development  in  the  treated  and 
control  cultures  was  very  similar.  In  Crone's  solution  very  few  branches  had 
appeared  in  the  treated  culture.  On  this  day  the  cultures  were  finally  measured 
and  harvested  with  the  results  appearing  in  Table  13*  This  table  shows  that  in 
all  series  the  control  cultures  had  made  more  growth.  The  carbon  dioxid  has  not 
affected  the  plants  in  the  various  media  to  the  same  degree. 

VII.  Experiments  in  Sand  Cultures 

The  striking  increased  growth  of  the  roots  of  beans  in  aerated 
cultures  of  Shive's  soliition  suggested  an  inquiry  into  their  response  to  increased 
oxygen  supply  in  solid  media. 

Ten  tall  glass  cylinders  were  filled  with  clean  sterile  sand  which  had 
been  mixed  with  sufficient  Shive's  solution  to  bring  the  moisture  content  up  to 
sixty  percent  saturation.  Beans  which  had  been  germinated  in  sphagnum  until  the 
radicles  were  2.5  cm.  long  were  then  planted  - one  in  each  cylinder.  These  were 
then  set  in  diffuse  daylight  in  a moist  atmosphere  until  the  hypocotyl  had 
elongated  and  the  first  leaves  began  to  unfold.  Four  of  the  cylinders  were  then 
attached  to  the  small  distribution  apparatus.  Oxygen  ms  passed  to  the  bottom  of 
the  vessels  through  long  glass  tubes  for  a period  of  ten  minutes  daily.  On  the 
eighth  and  fourteenth  days  the  oxygen  was  run  continuously  for  twelve  hours.  Two 
of  the  remaining  cultures  were  attached  to  the  air  supply  for  a period  of  twelve 
hours  on  the  eighth  and  fourteenth  days.  The  remaining  cultures  received  no 


-26- 


treatment. 

The  surface  evaporation  and.  the  water  lost  by  transpiration  was  replaced 
on  alternate  days  in  the  first  week  and  daily  thereafter.  Half  of  the  water  wa3 
added  at  the  surface  of  the  sand  and  the  remainder  down  the  aeration  tube.  Since 
the  seedlings  were  chosen  when  very  young  the  desired  uniformity  was  not  obtainable 
Biweekly  measurements  of  the  leaf  length  and  leaf  breadth  revealed  no  superiority 
which  could  be  attributed  to  treatment.  After  eighteen  days  the  plants  were  taken 
down.  The  roots  were  washed  free  of  sand,  replaced  in  their  respective  vessels 
and  photographed  forty-eight  hours  after  (Plate  XI).  In  all  the  cylinders  treated 
with  oxygen,  the  roots  were  longer  than  in  the  controls.  The  controls  which  had 
been  treated  with  air  weekly  were  intermediate  in  development.  The  plants  were 
left  in  tap  water.  All  the  old  leaves  ’wilted  and  the  roots  di9d.  After  a week 
the  plants  had  all  produced  new  roots  and  leaves. 

The  results  indicate  that  better  development  of  the  root  system  i3 
attained  by  aeration  and  oxygenation.  In  order  to  increase  the  efficiency  of  the 
aeration,  long  narrow  vessels  were  chosen.  The  aerating  gases  thus  passed 
through  a long  narrow  column  of  sand.  This  at  the  same  time  involves  greater 
difficulty  in  securing  adequate  and  equal  distribution  of  the  moisture.  An 
attempt  to  overcome  this  was  made  by  adding  equal  quantities  above  and  below. 

There  remains  a possibility  that  uniform  moisture  distribution  was  not  attained 
in  the  control  cultures  and  that  the  shortness  of  the  roots  was  due,  in  part  at 
least,  to  this  consideration. 


-27- 


VIII. 


SUMMARY 


In  the  experiments  on  aeration  the  three  crops  studied  did  not  all 
respond  to  the  same  degree.  YMle  the  growth  of  corn  in  tap  water  was  comparative* 
ly  poor,  the  results  indicate  that  no  increased  growth  in  either  root  or  shoot  is 
obtained  by  continuous  aeration  or  aeration  for  short  periods  at  intervals.  The 
concentration  of  dissolved  oxygen  showed  no  correlation  with  growth  within  the 
limits  attained  by  aeration. 

In  Shive’s  solution  aeration  for  varying  periods  over  thirty-five  day3 
failed  to  produce  any  differentiation  in  either  roots  or  tops.  The  character  of 
the  roots  of  com  manifested  no  modifications  which  could  be  attributed  to 
aeration.  If  the  elongation  of  the  root  is  interferred  with  by  contact  with  the 
sides  of  the  vessel,  root  hairs  develop  occasionally  at  points  a short  distance 
behind  the  tip  of  the  roots. 

In  the  case  of  beans,  aeration  has  had  decided  effects  in  increasing 
the  dry  weight  of  both  tops  and  roots.  Beans  grown  to  maturity  in  Shive’s 
solution,  with  frequent  renewals,  showed  an  increase  of  19$  in  the  dry  weight  of 
the  tops.  The  roots  alone  increased  by  33$*  Up  to  flowering  time  plants  grown 
in  Shive’s  solution  without  renewal  showed  an  increase  amounting  to  20$,  while 
that  of  the  roots  was  60$.  Plants  grown  a week  longer  shewed  30$  and  S0$ 
respectively.  In  Crone’s  solution,  where  the  root  system  was  profoundly  modified, 
the  tops  increased  by  l6$  and  the  roots  decreased  by  6$.  Although  individual 
variations  were  considerable,  they  are  overshadowed  by  the  effects  of  the  treat- 
ment. The  character  of  the  roots  in  treated  and  control  cultures  was  the  same 
for  a constant  solution.  The  root  development  in  Crone’s  solution  was  exceedingly 
poor. 

In  the  case  of  barley,  aeration  in  Shive’s  solution  has  produced  an 
increase  of  19$  in  the  total  dry  weight,  and  l4$  in  the  roots  alone,  aeration 


-28- 


did  not  appear  to  affect  the  character  of  the  roots  or  the  production  of  root  hairs  , 
Then  the  partial  pressure  of  the  dissolved  oxygen  is  increased  above  that 
of  saturation  at  normal  temperatures,  no  increased  growth  has  been  noted  in  corn, 
beans  or  barley.  This  appears  to  be  true  whether  the  higher  pressure  be  obtained 
by  frequent  renewals  of  the  solution  or  by  bubbling  oxygen  through  it.  With 
barley  grown  in  tap  water,  the  results  obtained  indicate  that,  while  there  is 
sufficient  oxygen  in  water  containing  sis  parts  per  million  of  oxygen,  the  process 
of  growth  is  hindered  when  this  pressure  falls  as  low  as  .2jp  p.p.M. 

Carbon  dioxid  has  proved  toxic  to  corn,  beans  and  barley  in  high  con- 
centrations over  short  periods  of  time.  Concentrations  up  to  fifteen  percent 
saturation  have  not  been  found  to  affect  the  development  of  corn  seedlings  ad- 
versely. The  after  effects  of  this  gas  are  noticeable  in  all  cases.  The  rate  of 
acceleration  of  growth  after  treatment  is  dependent  on  the  length  of  the  time 
of  treatment.  If  this  be  short,  the  recovery  is  rapid  until  the  normal  rate  is 
regained. 

In  all  the  cases  considered  the  roots  were  profoundly  affected.  The 
degree  varied  from  entire  suppression  of  branches  and  elongation  to  only  a slight 
retardation  of  the  rate  of  growth.  In  the  case  of  barley  the  nature  of  the 
solution  appeared  to  affect  the  rate  and  manner  of  recovery,  In  all  the  cases  in 
which  seedlings  were  used  the  roots  continued  to  function  and  maintained  the 
transpiration  current. 

In  these  experiments  the  lack  of  oxygen  may  have  been  a contributory 

cause . 

The  hydrogen-ion  concentration  has  not  been  found  to  be  materially 
affected  by  aeration. 


. $ I .*v  M 


“25- 


CON CL? SIGNS 

In  the  experiments  reported  aeration  has  not  produced  increased  growth 
in  com.  The  growth  of  this  plant  is  not  retarded  or  stimulated  "by  aeration  or 
oxygenation.  This  plant  appears  indifferent  to  any  increase  of  the  dissolved 
oxygen  above  six  parts  per  million. 

Aeration  and  oxygenation  do  not  modify  the  character  or  the  amount  of 
root  growth.  In  saturated  solutions  carbon  dioxid  exercises  a toxic  effect  on 
seedlings  of  com.  Solutions  containing  up  to  fifteen  percent  of  this  gas  pro- 
duced no  effect  within  one  week. 

Beans  respond  to  aeration.  The  amount  of  increase  in  dry  weight  varies 
with  the  length  of  the  growth  period.  The  roots  show  a greater  percentage  in- 
crease than  the  entire  plant.  The  nature  cf  the  solution  in  which  the  plants  are 
grown  affects  the  degree  of  response  to  aeration.  ITo  increased  growth  is  produced 
in  young  plants  if  the  partial  presstire  of  the  oxygen  be  increased  above  saturation 
under  normal  atmospheric  conditions.  In  saturated  solutions  carbon  dioxid  is  very 
toxic  to  well  developed  bean  plants. 

Barley  responds  to  aeration.  The  character  of  the  roots  is  not 
modified  by  aeration.  The  development  of  seedlings  is  retarded  in  solutions  con- 
taining less  than  two  parts  per  million  of  dissolved  oxygen.  Seedlings  are 
impartial  to  any  increase  of  the  dissolved  oxygen  above  saturation  under  normal 
atmospheric  conditions.  The  composition  of  the  nutrient  solution  determines  the 
character  of  the  root  growth.  Aeration  has  not  been  found  to  affect  it. 

If  the  nutrient  solution  be  saturated  with  carbon  dioxid  for  short 
periods  growth  is  retarded  and  the  roots  become  modified.  The  nature  of  the 
nutrient  medium  affects  the  rate  of  recovery  after  treatment. 


-30 


LITERATURE  CITED 


1.  American  Public  Health  Association,  1520. 

Standard  Methods  for  the  Examination  of  Water  and  Sewage. 

2.  Arker,  J.  1901 

Die  Bieenflussung  des  Wachstums  durch  das  umgebende  Medium. 

Diss.  Erlangen  1500.  Bot . Con.  &7>  P*  ^33 « 

3.  Bergman,  H.  F.  1520. 

The  Relation  of  Aeration  to  the  Growth  end  Activity  of  Roots  and  its 
Influence  on  the  Ecesis  of  Plants  in  Swamps. 

Ann.  Bot.  34,  P*  13* 

4.  Cannon,  W.  A.  1521. 

Root  Growth  in  Relation  to  a Deficiency  of  Oxygen  or  an  Excess  of  Carbon 
Dioxid  in  the  Soil. 

Carnegie  Inst.  Wash.  Year  Book  20,  p.  49* 

5.  Clark,  W.  M.  IS 20. 

The  Determination  of  Hydrogen-ions. 

(Williams  and  Williams,  Baltimore) 

6.  Clements,  F.  E.  1921. 

A.eration  and  Air  Content. 

Carnegie  Inst.  Wash.  Publication  No.  315* 

7.  Day,  G.  E.  1906. 

Experiments  on  Aeration. 

Ann.  Rept.  Ont . Agr.  College,  31 , p.  37. 

S.  Day,  0.  E.  1907. 

Aeration  of  Soils. 

Ann.  Rep.  Ont.  Agr.  College,  32,  p.  3&. 

9.  Free,  E.  E.  1917* 

The  Effect  of  Aeration  on  the  Growth  of  Buckwheat  in  Water -cultures. 

The  Johns  Hopkins  University  Circular,  No.  293 » New.  Ser.  No.  3»  P«  192. 

10.  Gillespie,  L.  J.  1520. 

Colorimetric  Determination  of  Hydrogen-ion  Concentration  without  Buffer 
Mixtures,  with  Especial  Reference  to  Soils. 

Soil  Sci.  9 1 P»  H5» 

11.  Hall,  A.  D. , Brenchley,  W.  E. , Underwood,  L.  M.  1513* 

The  Soil  Solution  and  Mineral  Constituents  of  the  Soil. 

Phil.  Trans.  Roy.  Soc.  Lond.  Series  B,  204. 

12.  Hole,  R.  S.  and  Singh,  P.  1914. 

Ecology  of  Sal  Part  1.  Soil  Composition,  Soil  Moisture,  Soil  Aeration. 
Indian  Forest  Records  5,  pt . 40  p.  1. 

Hole,  R.  S.  and  Singh,  P.  1916. 

Ecology  of  Sal.  Part  III.  Soil  Aeration  and  Water -cultures.  Ibid  5, 

pt.  4.  43. 


13. 


-31- 


l4.  Howard,  A.  and  Howard,  G.  L.  C.  1920. 

Some  Aspects  of  the  Indigo  Industry  in  Bihar.  Mem.  Dept.  Agr.  India, 

Bot.  Ser.  11,  p.  1. 

15 » Leather,  J.  W.  1915* 

Soil  Gases. 

Mem.  Dept.  Agr.  India,  Chem.  Ser.  4,  p.  $85 • 

l6.  Livingston,  B.  E.  1919  (Edited  by) 

A Plan  for  Cooperative  Research  on  the  Salt  Requirements  of  Representative 
Agricultural  Plants. 

17«  Russel,  E.  J.  and  Appleyard,  A.  1915* 

The  Atmosphere  of  the  Soil.  Its  Composition  and  Causes  of  Variation. 

Jour.  Agr.  Sci.  7:1*  P«  240. 

18.  Stiles,  jf,  and  Jorgensen,  I. 

Observations  on  the  Influence  of  Aeration  of  the  Nutrient  Solution  in 
Water-culture  Experiments  with  Some  Remarks  on  the  Water-culture  Method. 
New  Phytolcgist  l6.  180. 

19.  Stone,  G.  E.  1906. 

In  Report  of  the  Botanist. 

Eighteenth  Ann.  Rpt.  Hatch  Expt.  Sta.  p.  124, 

20.  Wacker,  J.  1898. 

Die  Beeinfluessung  des  Wackstums  der  WhrzeJn  durch  das  umgebende  Medium. 
Jahrb.  Uss.  Bot.  32,  p.  71  • 


-32- 


Table  1. 


A. 

Tap  Wat  er 

From  analysis  of  Illinois  Water  Survey 
April  27th,  1920.  No.  42306 


Salt  3 

p.p.ra. 

NalTCh' 

1.70 

Nap SO4 

1.09 

Na^CO^ 

66.14 

(NH^pCO-j 

7.63 

M9CO3 

95.96 

CaCO^ 

159.90 

F92O3 

3.49 

AC  ^03 

3.19 

SiOp 

22.10 

Silicious 

bases 

230. 

B* 


Crone  * s 

solution  (Modified) 

KNO3 

1.00 

M3SO4 

.25 

CaS04 

.25 

K0EPO4 

.25 

FeCsj 

.04  (Stile3  used 
.10) 

Distill 

ed  water  1000. Occ  (Stiles 

used  tap) 

Total  363«87  parts  per  million 

Table  2. 

Results  of  Aeration  of  Com  Grown  in  Tap  Water 
(Period  23  days  from  sowing) 

Treatment  Average  height  Green  weight  Dissolved 


inches 

Tops 

0? 

Not  aerated 

23.2 

3.2S 

5.9 

Aerated  10  minutes  on 
alternate  days 

24.1 

3.32 

6.3 

Aerated  1 hour  daily 

22.3 

3.27 

7.3 

Aerated  12  hours  daily 

23.8 

3.17 

7.4 

Continuous  aeration 

21.7 

3.22 

7.6 

-33- 

Table  3 


Effects  of  Aeration  on  Corn  Grown  in  Tap  Water 
(Period  of  growth  22  days) 


No. 

Number 

Leaves 

Height 

Inches 

Length  Roots 

Green  Weight 

Dry  Weight 

Great  - 
est 

Aver- 

age 

Tops 

Roots 

Tops 

Root  3 

Total 

A1 

5 

IS 

16 

9 

2.59 

1.11 

.280 

.0700 

.350 

A2 

5 

19-3 

26 

13 

2.65 

1.31 

•313 

.0955 

.408 

A3 

5 

20.1 

15 

12 

2.58 

1.27 

.286 

.0370 

•373 

Mean 

•377 

N1 

5 

17. s 

14 

11 

2.33 

1.29 

.258 

.0920 

.350 

N2 

5 

20.4 

15 

12 

2.39 

1.26 

.282 

.0865 

.368 

N3 

5 

19.1 

16 

12 

2.43 

1.20 

.291 

.0805 

.371 

Mean 

.363 

Table  4. 

Effects 

of  Aeration  on 

Corn 

Grown  in  Shivefa  Solution 

(Period  of  Growth  40  days) 

Solution  changed  on  12th,  20th, 

28th,  36th  days 

Number 

Number 

Height 

Total 

Leaf 

Green  Weight 

Dry  Weight 

No. 

Leaves 

Leaves 

Inches 

Length 

Tops 

Roots 

Tops  Roots 

Total 

SI 

5 

S.2 

25.8 

147.5 

13.6 

4.5 

1.284  .198 

1.482 

S2 

4 

S.2 

25.2 

136.5 

11.9 

3.8 

1.262  .192 

1.354 

S3 

4 

S 

25-7 

142.3 

13.8 

3.9 

1.311  .186 

1.497 

s4 

5 

8.2 

26 

148.0 

l4.l 

4.1 

1.364  .201 

1o65 

S5 

6 

8.2 

25.2 

133 

.2 

12.2 

4,0 

1.271  .197 

1.468 

s6 

5 

8 

24.5 

l4l.O 

12.4 

3.9 

1.232  .191 

1.423 

'J 


-31*- 

Table  5 


Daily  Analysis  for  Dissolved  Oxygen  of  Six  Cultures  of  Com  in  Tap  Water 

(Oxygen  in  parts  per  million) 


Treatment 

Days  after 

setting  up 

8 9 10 

11 

12 

13 

15 

16 

17 

18 

19 

20 

.Aerated 

Al 

8.2  6.0  6.9 

6.2 

5.8 

5-2 

7.9 

6.9 

7.9 

6.9 

6.4 

5.8 

A2 

8.7  6.2  6.3 

5.8 

4.9 

5-1 

7.7 

6.8 

8.4 

7.2 

6.1 

6.3 

A3 

8.2  6.7  6.1 

5-7 

4.3 

i — 
IT\ 

7.7 

6.7 

7.6 

7-2 

6.2 

5.4 

Ave. 

8.3“573  £74 

5-9 

5.0 

5-3 

7-8 

6.8 

8.0 

7.1 

6.2 

5.8 

Not  aerated 

N1 

5.2  4.6  2.9 

2.1 

1.3 

.8 

4.3 

2.3 

1.6 

•7 

.6 

.4 

N2 

7.9  4.8  2.8 

2.1 

• 9 

.7 

3.6 

1.8 

1.8 

.8 

1.2 

.3 

N3 

6.1  4.9  3.1 

2.4 

1.2 

.9 

3.7 

2.1 

1.9 

1.1 

•7 

•5 

Ave. 

nPT"4.7  2.9 

2.2 

1.3 

.8 

3.9 

2.1 

1.7 

.8 

0.8 

.4 

mter  added 

.6  .25  .3 

.6 

• 3 

.3 

1.3 

.2 

.2 

•3 

Carbon  dioxide 

Aerated 

Not  aerated 

•5 

3.2 

--35- 


Table  6. 

Effects  of  Continuous  Aeration  on  Beans  Gro wn  to  Maturity  in  Shive’s  Solution 
Solution  Renewed  on  l6th,  24th,  2 9th,  38th  days 
Period  of  Growth  February  1 - April  g 


Treatment  Number 

Green 

Tops 

Wei  ght 
Roots 

Tops 

Dry 

Root3 

Weight 

Total 

Seeds 

Aerated  1 

14.7 

2.5 

3*4g2 

.218 

3.70 

1.63 

2 

23.  og 

3.8 

3.260 

.216 

3.836 

2.31 

3 

15-92 

2.52 

3012 

.193 

3.505 

1.64 

4 

11.75 

2.04 

3-281 

.211 

3.492 

1.4i 

5 

14.98 

3.52 

3.124 

.184 

3.403 

.70 

Ave. 

3‘53S 

Not  aerated  1 

17.8 

1.46 

2-971 

.169 

3.040 

1.684 

2 

20.72 

1.65 

3.174 

.174 

3.34s 

1.773 

3 

19.45 

1.70 

2.212 

.201 

2.413 

l.l6g 

4 

23.6 

2.24 

3.023 

.193 

3.216 

1.640 

5 

15.  lg 

2.21 

2.g71 

.187 

3.053 

1.21 

Ave 


3.015 


-36- 
Table  7« 

Effects  of  deration  on  Beans  Grown  in  Shive's 
Growth  Period  March  29  - May  1 , May  7 
Solution  not  Changed 

A.  Harvested  May  1. 

Solution 

Length  Roots 

Treatment  Number  Number  Greatest  Average 

Leaves 

Dry  Wei  ght 
Tops  Roots 

Total 

Aerated  1 

9 

15 

11.5 

1.304 

.172 

1.476 

2 

10 

14.5 

10 

1.262 

.159 

1.421 

3 

2 

16.3 

11 

.912 

.194 

1.106 

4 

9 

17 

13.5 

1.275 

.177 

1.452 

5 

9 

15 

12 

1.155 

.172 

1.327 

Ave. 

1.356 

Not  aerated  11 

2 

7 

5-5 

.204 

.100 

.304 

12 

9 

2.5 

6.0 

1.240 

.1062 

1.346 

13 

g 

10.5 

6.0 

1.033 

.1152 

1.14S 

14 

9 

9.5 

7-5 

1.136 

.1062 

1.342 

15 

9 

9 

7.5 

.244 

.119 

.963 

Ave. 

1.121 

B.  Har vested  M&y  7* 

Aerated  6 

is 

l4 

1.142 

.219 

1.361 

7 

13 

11 

1.637 

.247 

1.924 

2 

15.5 

13 

1.722 

.192 

1.926 

9 

15 

12.5 

1.779 

.230 

2.009 

10 

15 

13 

1.722 

.232 

2.026 

Ave. 

1.277 

Not  aerated  l6 

6 

5-5 

1.344 

.141 

1.425 

17 

7 

5-5 

1.120 

.112 

1.232 

18 

g 

5 

1.370 

.129 

1.499 

19 

g 

6 

1.210 

.121 

1.432 

20 

g 

4 

1.440 

.140 

1.580 

Ave. 

1.446 

— 

Table  3. 

Effects  of  deration  on  Beans  Grown  in  Modified  Crone *3  Solution 

Solution  Not  Changed 
Period  of  Growth  May  10  - June  6th 


Length 

Green  Weight 

Dry  Weight 

Treatment  Number 

Roots 

Tops 

Roots 

Tops 

Root  8 

Total 

Aerated  1 

2.25 

$.2 

•95 

.360 

.063 

.923 

2 

3 

2.57 

.35 

.341 

.072 

•913 

3 

2.25 

9* S3 

.32 

1.036 

.067 

1.103 

4 

2.75 

10.60 

1.01 

I.O56 

.034 

i.i4c 

5 

3 

10.74 

1.13 

1.112 

.092 

1.214 

6 

3-25 

9.73 

1.06 

1.C58 

.032 

1.142 

7 

3 

10.35 

.93 

1.137 

.069 

1.256 

Ave. 

1.099 

Not  aerated  1 

2.75 

10.17 

1.01 

1.090 

.032 

1.172 

2 

3.50 

S .55 

.76 

.350 

.074 

.924 

3 

3.25 

9.30 

1.04 

.311 

.034 

.295 

4 

3.50 

S.72 

•S3 

.632 

.063 

• 7**5 

5 

3.25 

10.11 

1.24 

1.022 

.092 

l.ll4 

6 

3.50 

3.95 

.34 

.792 

.033 

.373 

7 

3.50 

9.10 

.92 

.324 

.033 

• 907 

Ave. 

.946 

Shives  1 

9.25 

l4.0 

1.34 

1.670 

.143 

1.213 

ErC2  2 

10.5 

12.6 

1.21 

1-590 

• 137 

1.727 

Control 

Not  aerated  3 Not  harvested 

Ave.  1-77° 


I 


Effects 

“38- 

Table-9. 

of  Aeration  on  Barley  Grown  in  Shive’s 
Period  of  Growth  April  3 " J^y  29 

Solution  Changed  once  only  on  May 

Solution 

7 

Height 

Number 

Dry 

Weight 

Treatment 

Number 

Inches 

Leaves 

Tops 

Roots 

Total  per  jar 

Aerated 

1 A 

23.0 

17 

.S34 

E 

24,5 

24 

.942 

.282 

2.058 

2 A 

20.2 

17 

.837 

B 

24.1 

19 

.882 

.231 

1.950 

3 A 

26.1 

20 

.S6l 

B 

27.1 

IS 

.841 

.203 

1.905 

4 A 

B 

(diseased) 

5 A 

19.4 

23 

.916 

E 

24.0 

14 

.672 

.246 

1.834 

6 A 

24.2 

IS 

.791 

B 

20.1 

21 

.S42 

.291 

1.924 

Mean 

Average 

per  plant 

.9671 

Not  aerated  1 A 

21.2 

19 

•792 

B 

IS.  6 

16 

.463 

.227 

1.482 

2 A 

B 

(diseased) 

3 A 

19.2 

16 

.743 

B 

19.4 

17 

.771 

.215 

1.725 

4 A 

23.1 

IS 

.821 

B 

19.2 

15 

.621 

.244 

i.6s6 

5 A 

24.2 

19 

.864 

B 

21.3 

14 

.681 

.221 

1.766 

6 A 

23.5 

15 

.514 

B 

22.2 

16 

.726 

.191 

1.431 

Mean 

Average 

per  plant 

.8095“ 

“39- 

Table  10 

The  Effect 

of  Increased  Partial  Pressure 

of  Oxygen  on  Growth  of  Earley 

in  Distilled  Water,  Tap  Water,  Shive’s 

Solution  and  Crone* 3 

Solution 

Period 

of  Aeration  June  20 

- July  3 

Length  Roots 

No. 

Height  Green  Weight  Dr. 

wt. 

(mgs) 

Culture 

Greatest 

Average  Leaves 

Tops  (crus) 

tops 

Tops 

Roots  Total 

02 

APAl 

29 

26 

2.2 

14.70 

•95 

97 

34 

131 

APA2 

29 

25 

15.34 

•91 

92 

30 

122 

APA3 

27 

25 

15.64 

•87 

96 

35 

131 

APA4 

22 

24 

14.27 

•91 

92 

32 

124 

Ave. 

22 

25 

15.79 

.26 

94 

33 

127 

17.2 

apni 

24 

22 

2.2 

16.50 

.26 

92 

37 

129 

APN2 

26 

24 

14.90 

.91 

106 

37 

143 

APN3 

17 

16 

15.60 

.93 

94 

33 

127 

AH'l4 

22 

20 

15.20 

.22 

97 

4l 

122 

Ave. 

22 

21 

I5.O5 

.22 

97 

37 

132 

6.2 

TA1 

19 

19 

3.0 

12.64 

1.22 

112 

42 

160 

TA2 

23 

21 

22.06 

1.13 

ll4 

46 

160 

TA3 

21 

19 

22.02 

1.26 

129 

71 

200 

ta4 

19 

12 

24.66 

1.30 

132 

62 

192 

Ave. 

20 

19 

2T.25 

1.22 

123 

55 

178 

17.2 

TNI 

21 

20 

3.0 

21.00 

1.36 

139 

42 

187 

TN2 

26 

22 

20.20 

1.26 

137 

37 

174 

TN3 

32 

21 

23.20 

1.26 

138 

36 

174 

tn4 

25  _ 

22 

23.10 

I.23 

131 

5* 

129 

Ave. 

26 

21 

21.27 

1.27 

13F 

45 

179 

6.2 

CrAl 

l4 

13 

3.0 

25.20 

2.30 

176 

40 

216 

CrA2 

15 

14 

27*30 

1.96 

145 

42 

187 

CrA3 

l6 

15 

26.90 

1.94 

159 

39 

19s 

Ave. 

15 

T 4 

26767'“ 

2.07 

' 160 

40 

200 

17.2 

CrlTl 

l6 

l4 

3-0 

26.50 

2.26 

173 

45 

223 

CrN2 

15 

14 

25.20 

2.14 

160 

40 

200 

CrN3 

l6 

14 

24.60 

2.05 

145 

39 

124 

Ave . 

lF” 

14 

25.43" 

2.15 

T6l 

41 

202 

6.2 

ShAl 

23 

23 

3.0 

26.20 

2.13 

170 

35 

125 

ShA2 

31 

22 

25.70 

2.10 

164 

42 

206 

ShA3 

21 

19 

26.30 

1.98 

153 

39 

192 

Ave. 

27 

21 

26.47 

2.07 

162 

39 

' 194" 

11F+ 

ShNl 

22 

17 

3.0 

27.30 

1.99 

162 

38 

200 

ShN2 

23 

21 

26.20 

2.02 

173 

36 

209 

SbN3 

22 

20 

23.70 

1.22 

157 

35 

192 

Ave. 

2k 

19 

2b.  40 

1.96" 

164 

3o 

200 

2.1 

-4  o ~ 


Table  No.  11. 

Effects  of  Saturation  with  C02  For  Short  Periods,  on  Growth  of  Com  in 


Tap  Water 

(Height  measured  in  centimeters) 


Time 

in 

Hours 

0 17 

29 

43 

96 

120 

144 

168 

192 

264 

No.  1 

4.82 

5.42 

6.24 

7.58 

12.20 

15.8 

18.8 

20.4 

22.45 

30.08 

No.  2 

4.85 

5.40 

6.70 

8.50 

15.14 

19.99 

22.5 

24.5 

26.8 

35.0 

No.  3 

4.12 

5.10 

6.32 

7.60 

13.30 

17.1 

18.7 

19.2 

20.8 

26.2 

No.  4 

4.96 

6.02 

7.60 

9.46 

16.30 

20.1 

22.6 

24.7 

28.0 

33.5 

Increments 

No.  1 

.6 

.82 

1.34 

4.6 

3.6 

3. 

1.6 

2.0 

7.6 

CM 

• 

O 

JZ! 

.5 

1.30 

1.8 

6.6 

4.8 

2.5 

2.0 

2.3 

8.2 

to 

. 

o 

a 

.98 

1.2 

1.3 

5.7 

3.8 

1.6 

.5 

1.6 

5.4 

No.  4 

1.1 

1.6 

1.9 

6.84 

3.8 

3.8 

2.1 

3.3 

5.5 

/ 


Effect  of  Low  Concentration  of  CO2  on  Growth  of  Corn  Seedlings  in  Tap  Water 


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2.2  T T 2.K  2.1 


Table  No.  13 


-42- 


Effects  of  Carbon  Dioxid  on  the  Growth  of  Barley  in 
Various  Solutions 
Period  of  Growth  20  days 


Culture  and 
Solution 

No  of 
Leaves 

Ht. 

cms. 

Length  Root 3 
cxns. 

Green  wt. 
grms. 

Dry  wt. 
mgs. 

Difference 

API 

2.5 

IS.  2 

IS 

AP2 

3.8 

IS.  6 

31 

T1 

3 

23.0 

19 

1.72 

193 

T2 

3 

26.2 

4o 

2.6 

241 

47 

Shi 

4 

31 

20 

3.3 

330 

Sh2 

4 

32.2 

24.1 

3.75 

365 

35 

Crl 

4 

26.1 

9 

2.S 

23S 

Cr2 

4 

31.4 

l4 

3.9 

340 

32 

Cr3 

3 

25 

9 

2.64 

Cr4 

3-2 

29.1 

12 

2.56 

ob 

ft 


Distribution  apparatus  used  in  minor  experiments. 


-44' 


<s: 


OJ 

U) 

£ 


Method  of  setting  up  corn  in  Experiment 


. 


' 


■ 


i O C 


Fig*  3*  Effects  of  carton  dioxid  on  corn  seedlings. 


-46 


'late  i.  Distribution  apparatus  as  used  to  test  effects  of  increased  partial  pressure  of  oxygen  on  barley 


-47- 


Plate  2.  Method  of  setting  up  barley. 


-4?- 


Q. 


Plate  3.  Beans  grown  to  maturity  in  Shivs’ s solution.  Solution 
not  changed. 

A-  not  aerated 
B.  aerated. 


-50- 


Plat©  5*  Beans  grown  in  Stove’s  solution.  Solution  net  changed.  Hot  aerated. 


Plata  6.  Comparison  of  root  systems  in  Sieve’s  and  Crone’s  solution. 


-52- 


Plate  7*  Barley  grown  On  Modified  Crone’s  solution.  Two  on  left  continuously  aerated.  On  right  net  aerated 


Plate  0.  Barley  grown  in  Shave’s  (R- C ) solution.  Two  on  left  aerated.  Two  on  ri :;ht  not  aerated 


Plate  9.  Barley  grow n in  Tap  water.  Two  on  left  aerated.  Two  on  right  not  aerated 


-55- 


Plate  10.  Barley  grown  in  distilled  water.  Two  on  left  aerated.  Two  on  right  not  aerated 


Plate  XI.  Effect  of  Oxygen  and.  Aeration  on  Beans  grown  in  moist  sand. 

1£  aerated  once  weekly,  3 ” ° oxygen  daily;  7 - 10  controls. 


